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Re: Performance: g++ Cygwin vs. other compilers (copying char[] to vector)


At 08:48 AM 7/18/2004, Alex Vinokur wrote:


"Tim Prince" <tprince@computer.org> wrote in message 6.0.1.1.0.20040718063702.01f796e8@imap.myrealbox.com">news:6.0.1.1.0.20040718063702.01f796e8@imap.myrealbox.com...
> At 05:00 AM 7/18/2004, Alex Vinokur wrote:
>
> >Hi,
> >
> >How to explain so considerable difference in performance: g++ Cygwin vs.
> >other compilers in tests below?
[snip]


> I don't find your compile options, or whether you have profiled.  For g++
> under cygwin,
[snip]

g++ *.cpp -o cps_cyg.exe   // g++ Cygwin
g++ -mno-cygwin *.cpp -o cps_mgw.exe  // g++ Mingw
gpp *.cpp -o cps_dj.exe  // g++ Djgpp
cl /EHsc *.cpp -o cps_ms.exe   // C++ Microsoft
dmc -I. -IC:/dm/stlport/stlport -Ae *.cpp -o cps_dm.exe  // C++ Digital Mars

Microsoft C default is a good compromise between compilation speed and performance. g++ Cygwin aims for compilation speed and no transformations which inhibit debugging. Performance simply is not comparable without normal optimization:
g++ -O3 -Drestrict=__restrict__ -funroll-loops -march=pentium4 -mfpmath=sse *.cpp
CL /EHsc /Ox /arch:SSE2 *.cpp
I have no idea about Digital Mars, but STLport does have more optimization than MS.
Nor do I know if any of your versions of g++ tinker with default optimization.
I believe clock() is implemented differently between cygwin and msvcrt, and you may have additional variations represented here.


Tim Prince


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